Vasculitis is defined by the presence of inflammatory leucocytes (white blood cells) in the vessel walls with damage to adjacent structures. Loss of vessel integrity can lead to bleeding. Historically, vasculitis was and remains subdivided into three categories which relate to the size of the affected vessel: small vessel, medium vessel, and large vessel. Both arteries and veins are involved. It is generally accepted in the medical community that the exact mechanism of many of the following disorders is yet to be defined. More recently, the presence or absence of an antineutrophil cytoplasmic antibody (ANCA) has refined the classification. Examples of the types of vasculitis are listed in Table VI and are further described below
The classic treatment for many of these vasculitides is administration of glucocorticoids, which are often taken for prolonged periods of time. Therapy is dependent upon the nature and extent of the disease process and may include the non-steroidal anti-inflammatory agents, antihistamines, cytotoxic drugs such as cyclophosphamide, or immunosuppressives such as methotrexate. Many of these agents, particularly when taken over extended periods of time, produce significant side effects such as bone marrow suppression (leucopenia, thrombocytopenia), secondary malignancy, sterility, interstitial pulmonary fibrosis, infection, and steroid induced diabetes mellitus which in certain cases are worse that the primary disease itself.
There exists an important unmet need for a therapeutic approach for treating vasculitis and related disorders, including treatment regimens that address one or more of the underlying pathologic mechanisms and/or relieve any of the overt symptoms thereof.